JP2003293227A - Method for producing carbonaceous fiber and the resulting carbonaceous fiber, and activated carbon fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an industrially advantageous method for producing a PVA-based carbonaceous fiber or PVA-based activated carbon fiber with high uniformity in a short time while suppressing precursor fiber contraction, and to provide the carbonaceous fiber or activated carbon fiber obtained by such a method. <P>SOLUTION: The carbonaceous fiber is produced by weight reduction of a PVA-based fiber as a raw material to 60-85 wt.% under tension followed by carrying out a carbonization treatment. The activated carbon fiber is produced by activating said carbonaceous fiber. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing carbonaceous fibers, carbonaceous fibers obtained by the producing method, and activated carbon fibers obtained by activating the carbonaceous fibers. More specifically, in a method for producing carbonaceous fiber using polyvinyl alcohol fiber (hereinafter, polyvinyl alcohol is abbreviated as PVA) as a raw material, 60% by weight or more under tension 8
A method for producing a carbonaceous fiber, which comprises reducing the weight to 5% by weight or less, and then performing a carbonization treatment, a carbonaceous fiber obtained by the producing method, and activated carbon obtained by activating the carbonaceous fiber. Regarding fibers.

The carbonaceous fibers and activated carbon fibers obtained by the present invention are suitably used for various electrode materials, heat insulating materials, adsorbent materials, flameproof materials and the like. Activated carbon fiber is also suitable for applications such as water purification, air purification, gas adsorption, water treatment, solvent recovery, decolorization, cigarette filters, clean room filters, blood purification, and further for secondary batteries, electrolytic capacitors, and electric batteries. It is also useful for electrode material applications such as multilayer capacitors.

[0003]

2. Description of the Related Art Up to now, many reports have been made on carbon fibers made of polyvinyl alcohol resins or PVA fibers as raw materials, or activated carbon fibers activated by these. Specifically, Japanese Examined Japanese Patent Publications 38-20353 and 40-
9061, 45-31707, JP-A-48-1
423, 48-39724, 48-41041, 48-41042, 49-13430, 49-24.
897, ibid. 50-35431, ibid. 50-52320, ibid. 50-52321, ibid. 51-38525, ibid. 53-11.
4925, 59-187624, 61-47827.
However, it has not been industrialized yet for the following reasons.

Japanese Patent Publication No. 38-20353 discloses a PV.
Disclosed is a method for producing a carbonaceous material, which includes a step of heating a molded product such as an A-based resin or fiber at a temperature of 400 ° C. or lower in an oxidizing atmosphere. In the manufacturing method,
Regarding the heating temperature in the oxidizing atmosphere, since the thermal decomposition temperature is around 200 ° C., it is described that the heat treatment is preferably performed in the oxidizing atmosphere at a temperature lower than the thermal decomposition temperature. Although heat treatment at 200 ° C. or 180 ° C. is illustrated in the examples, all of them are methods that require a very long time of 15 hours or more to sell a carbonaceous material. Therefore, from the viewpoint of industrialization, low productivity is a problem, and it is obvious that the method is not industrially advantageous.

Japanese Patent Publication No. 40-9061 discloses a method for producing a fibrous carbon material by reacting a polymer fiber containing vinyl alcohol or a derivative thereof with halogen or a compound thereof and then firing the polymer fiber. There is. It is described that this production method has an effect of improving yield and improving mechanical properties. However, as is clear from the examples, since a large amount of halogen is used in such a method, in addition to the necessity of supporting the apparatus by using halogen, there is concern that the apparatus may be corroded by hydrogen halide during heat treatment. However, it is not a recommended method from the viewpoint of industrialization.

In Japanese Patent Publication No. 45-31707, vinyl alcohol fiber is heated at a temperature between 100 ° C. and 300 ° C. in an atmosphere containing hydrochloric acid gas and vapor of a non-oxidizing acid, and then air. 1 in other oxidizing atmospheres
Heating at a temperature between 50 ° C and 300 ° C, and then
A carbonized fiber obtained by heating at a temperature between 300 ° C. and 1000 ° C. in a non-oxidizing atmosphere and a method for producing the same are disclosed. And according to this method, shrinkage suppression
It is described that it is effective in improving the yield. However, from the viewpoint of industrialization, there is concern that the apparatus may be corroded during the heat treatment in a hydrochloric acid gas atmosphere, and regarding the heat treatment in the oxidizing atmosphere thereafter, as is clear from the examples,
It takes a long time of 3 hours at 200 ° C. or 16 hours at 230 ° C., and it cannot be said that the productivity is excellent.

Japanese Unexamined Patent Publication (Kokai) No. 48-1423 discloses that a synthetic fiber composed of 10 to 35% by weight of polyvinyl chloride and 90 to 65% by weight of PVA is preoxidized in air at 150 to 235 ° C. for 5 to 10 hours. And then 250-3 in nitrogen
A method for producing carbon fibers is disclosed, which is pre-fired at 50 ° C. for 2 to 5 hours and further carbonized to 1200 ° C. in 5 to 7 hours. It is described that this manufacturing method is effective in suppressing shrinkage and shortening production time. However, there is concern that the hydrochloric acid gas generated from polyvinyl chloride during heat treatment may corrode the device. In terms of productivity, the total heat treatment time is as long as 10 hours or more as far as the Examples are concerned, and it cannot be said that this is a rational production method.

Japanese Unexamined Patent Publication (Kokai) No. 48-39724 discloses a PVA-based carbon fiber for carbonizing a fiber obtained by wet spinning a PVA aqueous solution having an average degree of polymerization of 2000 or more in a solidifying bath of an aqueous solution mainly containing caustic alkali. A manufacturing method is disclosed. According to this manufacturing method, it is described that the strength and flexibility are effective, but there is little description about the heat treatment conditions, and in Examples, the temperature is set to 210 ° C. or less in air for a long time (5
Only ~ 15 hours) is mentioned. Therefore, the productivity is low, the resin, the spinning method, etc. are limited, and since it is solidified with an aqueous solution mainly containing caustic, it is extremely dangerous and cannot be said to be a method recommended from an industrial viewpoint. .

JP-A-48-41041 discloses that a vinylidene chloride component obtained by mixing and spinning an aqueous emulsion of vinylidene chloride homopolymer or vinylidene chloride copolymer and PVA is 30% by weight or more and the PVA component is A method for producing a PVA-based carbon fiber in which 30% by weight or more of carbon is carbonized is disclosed. According to this manufacturing method, it is described that the process and time are shortened, and the yield is improved. However, during the heat treatment, corrosion of the device by hydrochloric acid gas which is a decomposition gas generated from polyvinylidene chloride is caused. I'm worried. Further, the spinning method and the like are also limited, and it cannot be said that the method is industrially advantageous.

JP-A-48-41042 discloses a PV.
A method for producing a PVA-based carbon fiber in which a carbon-carbon double bond is introduced into an A-based fiber, chlorine or / and bromine is added thereto in an amount of 10% by weight or more, and then carbonized, is disclosed. According to this method, it is described that the process and time are shortened and the yield is improved. However, a halogenation process is required, and it is necessary to cope with the apparatus. Further, there is a concern that the hydrogen halide may corrode the device during the heat treatment, and the manufacturing cost is increased because the device is used. Therefore, this method is considerably disadvantageous from an industrial point of view.

JP-A-49-13430 discloses a PV.
In producing carbonaceous fiber by heating A-based synthetic fiber,
A method for producing carbonaceous fibers is disclosed in which PVA-based fibers are pretreated with a hydrophobic organic solvent having a dielectric constant of 10.0 or less. According to this production method, it is described that it is effective in improving the soft texture, but a pretreatment step with an organic solvent is required, and an apparatus therefor is also required. Regarding heat treatment conditions, as seen in the examples, heat treatment is performed for 5 hours or more, and it is hard to say that this is an advantageous method in view of productivity.

JP-A-49-24987 discloses that a PVA fiber containing at least one of sodium hydrogensulfate and potassium hydrogensulfate or a product thereof is heated in an oxidizing atmosphere at a temperature of 220 ° C. or lower, A method for producing a PVA-based carbon product which is then fired in a non-oxidizing atmosphere is disclosed. And according to this manufacturing method, yield improvement,
It is described that there are effects such as flexibility, high strength, and prevention of heat storage. However, according to the examples, it is considered that the infusibilization is performed at a temperature of 220 ° C. or lower, so that the reaction rate of infusibilization is slow and the heat treatment requires a long time, but the heat treatment requires a long time of 10 hours or more. However, it is not a realistic production method when productivity is taken into consideration.

In Japanese Patent Laid-Open Publication No. 50-35431, a heat-treated high-stretching and fine-fineness PVA-based synthetic fiber filament is used as a starting material, and a weight loss of 20 to 35% is achieved without strain in the presence of a dehydration catalyst. Carbon that is subjected to carbonization or graphitization treatment in an inert gas atmosphere containing no oxygen in a tension state after being subjected to a heat dehydration treatment for 1 to 5 hours in an oxidizing atmosphere at a temperature of 150 to 200 ° C. A method of making fibers is disclosed. According to this method, it is described that there is an effect on cost reduction by shortening the production time, but its application range is narrow because it is limited to heat-treated PVA with high stretching and fineness. As for the dehydrating agent, an example in which it is carried out only in a hydrochloric acid gas atmosphere is described in the examples, and there is a concern that the apparatus may be corroded. Further, the subsequent oxidation treatment also requires 1 to 5 hours, which is not an industrially advantageous method.

JP-A-50-52320 discloses a PV.
When producing carbon fiber using the A-based synthetic fiber filament as a starting material, the PVA-based fiber filament added with a dehydration catalyst of 3 to 20% by weight was reduced in weight by 20 to 35% in an inert gas atmosphere without tension. A carbon fiber that is subjected to heat dehydration treatment so that it is generated, then treated in an oxidizing atmosphere at a temperature of 150 to 200 ° C. for 1 to 5 hours, and then heat-fired in an inert gas under tension to perform carbonization or graphitization treatment. Is disclosed. It is described that this method is a method for producing a carbon fiber which has low pollution and can be treated in a short time, is low in cost, and has high performance, but according to the examples, the weight is 20 to 35%. About 4 hours are required for the process of heat dehydration treatment so that the reduction occurs. Further, the oxidation treatment requires 1 to 5 hours, which is still insufficient from the viewpoint of shortening the time. Further, the subsequent heat treatment also requires a temperature rise, and there is a problem of melting when suddenly introduced into a high temperature of about 1000 ° C.

Japanese Patent Application Laid-Open No. 50-52321 discloses PV.
When producing carbon fiber using the A-based synthetic fiber filament as a starting material, the PVA-based synthetic fiber filament containing 3 to 20% by weight of a dehydration catalyst is reduced in weight by 20 to 35% in an oxidizing atmosphere without tension. The method for producing carbon fibers is disclosed in which carbon fibers are heated and calcined in an inert gas under tension and then carbonized or graphitized. This method has low pollution and can be processed in a short time,
It is described as a low-cost and high-performance method for producing carbon fiber. However, according to an embodiment, 20 to
4 in the process of heat dehydration so that weight loss of 35% occurs
It takes about 8 hours, which is still insufficient from the viewpoint of shortening the time. Further, the subsequent heat treatment also requires a temperature rise, and there is a problem of melting when suddenly introduced into a high temperature of about 1000 ° C.

JP-A-51-38525 discloses a PV.
There is disclosed a method for producing a carbon fiber in which PVA is maintained in a swollen state, radiation-treated, and then fired when A is fired to produce a carbon fiber. And, it is described that this method is effective in improving the yield by radiation treatment. However, according to this method, the heat treatment time requires a long time which is not much different from the conventional method.
Moreover, from the viewpoint of safety, radiation shielding equipment is essential.
It is hard to say that this is an industrially advantageous method.

Japanese Patent Laid-Open No. 53-114925 discloses that
(1) PV prepared by adding an ammonium phosphate compound as a dehydration reaction accelerator in an amount of 3 to 15% by weight based on PVA
A. A spinning raw yarn is dry-spun to produce a raw material fiber,
(2) Weight yield of the raw material fibers is 65% to 85%
The raw material fibers are heated and dehydrated at a temperature of 180 to 340 ° C., and (3) the dehydrated yarn is treated at a temperature of 600 to 1000 ° C. in an atmosphere of an inert gas containing water vapor. 10-35% weight yield to fiber
A method for producing an activated carbon fiber, which comprises activating treatment until It is described that according to this production method, activated carbon fibers having an excellent adsorption amount can be obtained with low pollution and in a short time.

However, in this method, the dry-spinning method is limited as the spinning prescription and the ammonium phosphate compound is limited as the dehydration reaction accelerator, and the post-attachment of the dehydrating agent gives activated carbon fibers having excellent adsorption performance. It has been shown that this is not possible, and there is a major limitation in this respect. Further, when the present inventors examined this method in more detail, it melts when rapid activation is performed and heat is stored when a large amount is charged, so a large amount of charging cannot be performed, and therefore productivity is low and industrialization From a point of view, it turned out to be still insufficient.

In Japanese Patent Application Laid-Open No. 59-187624, PVA fibers to which a dehydrating agent is attached or contained are heated until the weight loss becomes 35% or more, and dehydration and carbonization reaction are performed to form carbonaceous fibers. 80 steps and the carbonaceous fiber obtained
Disclosed is a method for producing activated carbon fiber, which comprises a step of rapidly activating at high temperature at a temperature of 0 to 1200 ° C. and in the presence of a slight amount of oxygen. Then, this method is described as a method for producing activated carbon fibers having excellent adsorption performance. However, when the present inventors conducted a supplementary test, it was found that when a large amount was charged, heat could not be stored because a large amount of heat was stored, and therefore the productivity was low and it was still insufficient from the viewpoint of industrialization. did.

Japanese Patent Application Laid-Open No. 61-47827 discloses PV.
A hollow activated carbon fiber obtained by carbonizing an A-based fiber is disclosed. It is described that this fiber has a unique physical property that has both the adsorptivity peculiar to activated carbon and the permeability of the hollow fiber wall.
It is described that the point is to dry-distill from 0 ° C to 1000 ° C within 5 minutes. However, regarding infusibilizing conditions before dry distillation, there is almost no description of specific conditions, and only a method of gradually heating and heating to 180 ° C. to 300 ° C. until blackening is described. Therefore, when the present inventors conducted a supplementary test, it was found that a large amount of heat cannot be stored because heat storage occurs, and therefore, this method also proves to be low in productivity.

As described above, although there have been many reports on carbonaceous fibers and activated carbon fibers using PVA as a raw material, they have not yet been industrialized. The reason is that fiber shrinkage during manufacturing is severe, process passability deteriorates and quality variation of the final product is likely to occur. Secondly, there are many processes and heat treatment requires a long time, so productivity is high. It is considered to be low.

[0022]

Therefore, the first object of the present invention is to suppress the shrinkage of PVA-based carbonaceous fibers or PVA-based activated carbon fibers, to produce in a short time, and to provide an excellent homogeneity in industry. Another object of the present invention is to provide a method for producing a PVA-based carbonaceous fiber or a PVA-based activated carbon fiber, which is particularly advantageous. A second object of the present invention is to provide a carbonaceous fiber obtained by such a production method, and a third object of the present invention is to further activate the carbonaceous fiber to produce activated carbon fiber. To provide.

[0023]

Means for Solving the Problems The inventors of the present invention have diligently studied and, when producing a carbonaceous fiber using a PVA-based fiber as a raw material, heat-treat it under tension and then carbonize it. Efficiently and easily obtain a target carbonaceous fiber, more specifically, after heat-treating the PVA-based fiber as a raw material under tension to a weight yield of 60% by weight or more and 85% by weight or less, By carbonizing this, attention is paid to the fact that the desired carbonaceous fiber can be obtained efficiently and in a short time, and by activating the carbonaceous fiber, the desired activity can be easily obtained. The inventors have found that carbon fibers can be obtained and have completed the present invention.

That is, the first aspect of the present invention is PVA.
A method for producing a carbonaceous fiber using a system fiber as a raw material, which comprises carbonizing after reducing the weight to 60% by weight or more and 85% by weight or less under tension.

The second invention of the present invention is a carbonaceous fiber obtained by this method, and the third invention of the present invention is obtained by activating the carbonaceous fiber in an oxidizing atmosphere or in the presence of water vapor. It is activated carbon fiber.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION The PVA-based fiber used in the present invention is obtained from a PVA-based resin obtained by saponifying polyvinyl acetate or a copolymer thereof which is usually used in the production of PVA. Further, it is obtained by decomposing a bulky vinyl ester having a side chain such as vinyl pivalate or vinyl formate or a vinyl ester having high polarity, or a homopolymer or copolymer of vinyl ether such as t-butyl vinyl ether, trimethylsilyl vinyl ether or benzyl vinyl ether. The PVA-based resin may be used as a raw material for the fiber.

Here, the comonomer unit of the copolymer can be divided into a unit which produces a vinyl alcohol unit by saponification or decomposition and a unit other than the unit. The latter comonomer unit is mainly used for modification. It is copolymerized and is used within a range not impairing the gist of the present invention. Examples of such a unit include olefins such as ethylene, propylene, 1-butene, and isobutene,
Acrylic acid and its salts, methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate,
Acrylic esters such as t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate, methacrylic acid and its salts, methyl methacrylate, ethyl methacrylate, n methacrylate
-Propyl, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-methacrylic acid
-Methacrylic acid esters such as butyl, 2-ethylhexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, acrylamide, N-methyl acrylamide, N-ethyl acrylamide, N, N-dimethyl acrylamide, diacetyl acrylamide Acrylamidopropanesulfonic acid and its salts, acrylamidopropyldimethylamine and its salts and quaternary salts, acrylamide derivatives such as N-methylolacrylamide and its derivatives, methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, N, N-dimethyl methacrylamide, diacetone methacrylamide, methacrylamide propane sulfonic acid and its salts, methacrylamide propyldimethylamine and its salts and quaternary salts,
Methacrylamide derivatives such as N-methylol methacrylamide and its derivatives, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, i-butyl vinyl ether, t
-Butyl vinyl ether, benzyl vinyl ether, dodecyl vinyl ether, vinyl ethers such as stearyl vinyl ether, acrylonitrile, nitriles such as methacrylonitrile, vinyl chloride, vinylidene chloride, vinyl fluoride, vinyl halides such as vinylidene fluoride, allyl acetate, Examples thereof include allyl compounds such as allyl chloride, maleic acid and salts and esters thereof, itaconic acid and salts and esters thereof, vinylsilyl compounds such as vinyltrimethoxysilane, and isopropenyl acetate.

The degree of saponification of the PVA resin is preferably 70 mol% or more, more preferably 90 to 99.99 mol%. Here, the degree of saponification is the ratio of vinyl alcohol units after saponification to units that can be converted to vinyl alcohol units by saponification in a vinyl acetate homopolymer or copolymer, and the residue is vinyl acetate. It is a unit.
The degree of polymerization of the PVA-based resin is preferably 1000 or more, more preferably 1700 or more. However, PVA-based resins having a degree of polymerization of more than 30,000 are generally difficult to produce, and are not necessarily suitable from the viewpoint of industrial production.

The method for producing the PVA-based fiber is not particularly limited, but a known wet spinning method, dry wet spinning method or dry spinning method can be adopted. What is the wet spinning method?
This is a method in which a spinning solution containing a polymer solution obtained by dissolving a PVA-based resin in an organic solvent or an aqueous solution obtained by dissolving the PVA-based resin in water is directly spun from a spinning nozzle into a solidifying bath, which is a dry-wet spinning method. Is a spinning method in which a gas space (air-gap) such as air or an inert gas is provided between a spinning nozzle and a solidifying bath, the gas is caused to travel for a specific distance, and then spun into the solidifying bath. .

The wet spinning method, in which the spinning nozzle is brought into direct contact with the solidifying bath to perform spinning, is suitable for spinning using a multi-hole nozzle because fibers can be spun without sticking even if the nozzle hole pitch is narrowed. On the other hand, in the case of the dry-wet spinning method in which an air gap is provided between the solidification bath and the spinning nozzle, and spinning is performed from the spinning nozzle through the gas, high-speed spinning is achieved due to the large elongation in the air gap portion. Are suitable. The dry spinning method is a spinning method in which a spinning dope, which is an aqueous solution obtained by dissolving a PVA-based resin in water, is spun directly into a gas from a spinning nozzle, and does not require a solidifying bath. . The spinning method as described above may be appropriately selected and adopted according to the purpose and use.

First, the wet spinning method and the dry wet spinning method will be described. Examples of the solvent for the PVA-based resin that constitutes the spinning solution include polyhydric alcohols such as glycerin, ethylene glycol, diethylene glycol, triethylene glycol and butanediol, and organic solvents selected from dimethyl sulfoxide (DMSO), dimethylformamide, diethylenetriamine and the like. Or, it is preferable to use a mixed solvent of two or more kinds thereof, and further a mixed solvent of these organic solvents and water. The spinning solution is PV
It is obtained by dissolving the A-based resin.

The concentration of the PVA resin in the spinning dope varies depending on the degree of polymerization, but is 5 to 30% by weight, especially 10 to 10.
It is preferably 20% by weight. If the concentration of the PVA-based resin is too high, the viscosity of the undiluted solution may be high and stable spinning may be difficult, and if the concentration is too low, the productivity tends to decrease, and the single fiber thickness Since variations (denier spots) are likely to occur, it is preferable to adjust the concentration within the above range. The spinning dope temperature is 80
~ 230 ° C is common.

If desired, other additives may be added to the spinning dope. For example, in order to extend the life of the spinneret during spinning and enhance the stability of the stretching process, one or more surfactants, inorganic decomposition inhibitors, dyes, pigments, etc. may be added to the spinning dope. In this case, the addition rate is preferably 20% by weight or less, particularly 0.1 to 5% by weight in order to suppress defective dewatering and solidification of Ishino. The type of surfactant may be any of nonionic type, anionic type, cationic type and amphoteric type, but when two or more types are used in combination, precipitation such as anionic type and cationic type occurs. Such a combination is not preferable. It is particularly preferable to use a nonionic surfactant.

It is also possible to form a cross-linked structure when discharging from the spinneret into the solidifying bath to make the structure of the cross section of the fiber uniform, for example, adding boric acid or borate salts to the stock solution. Can form a crosslinked structure. In this case, the boric acid or borate contained in the spinning dope is 0.
It is desirable to add it in an amount of 03 to 0.2% by weight, preferably 0.05 to 0.15% by weight. The spinning dope thus obtained is spun in a solidifying bath through a spinning nozzle by a wet spinning method or a dry wet spinning method.

As the solidifying liquid for solidifying the spinning dope and making it into fibers, there are solvent-based or aqueous solidifying liquids. The solvent-based solidifying liquid is preferably an organic solvent having solidifying ability with respect to PVA, such as alcohols such as methanol and ethanol, ketones such as acetone and methyl ethyl ketone. From the standpoint of spinnability, fiber performance, etc., the concentration of the stock solution for spinning in the solidification bath is 20 to 70% by weight, and further 25 to
It is more preferably 65% by weight, and the composition weight ratio of the solidifying solution / spinning stock solution solvent is preferably 25/75 to 85/15. Further, other additives may be added as long as the effects of the present invention are not impaired.

From the viewpoint of further reducing the solidification reaction rate to form a sufficiently uniform gel structure inside the fiber, the temperature of the solidification bath is preferably 30 ° C. or lower, particularly 20 ° C.
Hereafter, the temperature is preferably set to 15 ° C. or lower. By adopting such a method, fibers having a high degree of crystallinity can be obtained even when solidification is uniform in the cross-sectional direction and heat treatment or the like is not performed. From the viewpoint of reducing sticking between fibers and facilitating subsequent dry heat drawing, it is preferable to wet draw 2 to 10 times with the organic solvent contained in the Shinoshino that has been separated from the solidifying bath. It is preferable to perform wet stretching in the temperature range of -60 ° C.

Then, the fibers may be immersed in an extraction bath to extract the solvent. As the extractant, alcohols such as methanol, ethanol and propanol, acetone, methyl ethyl ketone, ether and water can be used. Then, if necessary, an oil agent or the like may be applied and dried.
From the viewpoint of increasing the strength of the PVA-based fiber, which is the raw material of the activated carbon, it is preferable to further carry out dry heat drawing, and it is particularly preferable to carry out dry heat drawing so that the total draw ratio is 6 times or more, preferably 8 times or more. . The total draw ratio is represented by the product of the wet draw ratio and the dry heat draw ratio.

The aqueous solidifying solution is not particularly limited as long as it has the ability to solidify the spinning dope, but from the viewpoint of processability and cost, it is preferable to use a solidifying solution using water as a solvent. Specifically, an aqueous solution of a salt having a dehydrating ability such as sodium sulfate (Glauber's salt), ammonium sulfate, and sodium carbonate is used. Aqueous solution concentration is 300
It is possible to select from g / liter (L) or more to a saturated concentration, but it is preferable that the concentration is as close to the saturated concentration as possible because the dehydration and solidification ability is high. Among them, it is preferable to use a saturated aqueous solution solidifying bath from the viewpoints of processability and cost. The temperature of the solidifying bath is 20 to 70
It is preferable that the temperature is set to 30 ° C, especially 30 to 50 ° C. When boric acid and borate salts are added to the spinning dope, the spinning dope is discharged into the solidifying bath to contain a substance such as sodium hydroxide for making the solidifying bath alkaline in order to develop a crosslinked structure. There is a need. For example, in the case of sodium hydroxide, the concentration in the solidifying bath is preferably 0.5 to 3% by weight.

The spinning dope discharged from the spinneret into the solidifying bath is dehydrated and solidified in the solidifying bath to form a yarn, and then separated from the solidifying bath to perform roller stretching about 1 to 4 times. Then, when boric acid or the like is added to the spinning dope and sodium hydroxide or the like is added to the solidification bath to develop a crosslinked structure, for example, sulfuric acid or the like for neutralizing and removing the alkaline compound adhering to the thread is contained. It is necessary to pass a neutralization bath containing the acid of. In this case, the concentration of sulfuric acid is 5
About 10 to 10% by weight is preferable. Then, in order to enhance the morphological stabilization of the Shinoshino, it is advisable to carry out wet heat stretching in a saturated aqueous solution bath of high temperature consisting of salts having the same dehydrating ability as the solidifying solution. The bath temperature is preferably 90 ° C. or higher, and the wet heat draw ratio is preferably about 1 to 3.

Next, in order to remove the salts, acids, boric acid and the like adhering to the Shinoshino by washing, the Shinoshino is introduced into a water washing tank and washed in running water until these contents in the fiber can be removed.
In the washing step, it is preferable to wash the thread under tension from the viewpoint of selectively removing inorganic salts on the fiber surface and inside the fiber, and from more effectively suppressing the swelling of the fiber. It is preferable to keep the tension constant. At this time, ultrasonic vibration may be applied to the Shinobu in the bath or the Shinobu may be moved up and down in the bath in order to selectively remove the inorganic salts on the fiber surface more quickly. From the viewpoint of effectively preventing swelling and sticking of fibers, the temperature of the cleaning liquid is 1
The temperature is preferably 0 to 70 ° C., and particularly preferably controlled to a constant temperature of 20 to 50 ° C.

If desired, an oil agent for preventing sticking may be attached to the thread after the washing step in order to suppress sticking between fibers which tends to occur after the drying step. As the attachment method, a conventionally known method, for example, a method of impregnating an oil agent tank with the oil agent to apply the oil agent, a method of contacting the roller surface with the oil agent with the thread agent, and the like can be adopted. As an oil agent component, it has good adhesion to PVA-based fibers and a drying temperature (100-
A material that does not solidify even at 150 ° C. and does not increase the inter-fiber friction coefficient of the PVA-based fiber, for example, a paraffin-based oil agent is preferable. Adhesion rate of oil agent is 1.2% by weight or less / P
VA, more preferably 0.8% by weight or less, and particularly preferably 0 to 0.5% by weight / PVA.

Next, the wet thread is dried. 80 drying
It is preferably carried out at a temperature of about 150 to 150 ° C., particularly about 100 to 140 ° C. Itoshino is dried, then stretched and wound up. The water content of Itoshino introduced into the drying process is 80 to 3
About 00% by weight / PVA, especially 90 to 200% by weight /
PVA, more preferably 100 to 150% by weight, is preferable in terms of prevention of sticking and drying efficiency. It is preferable that the moisture content of the dried shinobi is 1% / PVA or less.

After the drying step, the thread is further stretched to obtain a PVA fiber having excellent mechanical performance. The stretching method is not particularly limited, and generally applied stretching is adopted. The total draw ratio is 6 times or more, especially 7 times or more, and further 8
It is preferably double or more. Further, after stretching, various treatments such as heat treatment, shrinkage treatment, oil agent imparting treatment, and acetalization treatment may be carried out if necessary.

Next, the dry spinning method will be described. PV
A type resin is made into a water-containing chip having a concentration of 40 to 60% by weight,
Heat and melt with an extruder and degas. The temperature of the spinning dope is preferably 90 to 140 ° C. Such P
The VA spinning stock solution is pressurized and discharged from the nozzle hole into the air for dry spinning. Even if the nozzle hole has a circular shape, it may have a shape other than a circular shape, such as a flat shape, a cross shape, a T shape, a Y shape,
It may be L-shaped, triangular, square, star-shaped or the like. However, the above-mentioned T-shaped, Y-shaped, L-shaped and other modified cross-section fibers may be broken during the production, but even if the fibers are broken, the purpose and effect of the present invention are not significantly impaired.

After that, it is dried to almost dryness. In order to prevent foaming during drying, drying is performed at a temperature of 100 ° C. or lower, and when the drying is performed to a certain degree, 1
It is preferable to perform the drying completely at a temperature of 00 ° C or higher. After drying, 200-250 ° C, preferably 220-240 ° C
Stretching is performed at the temperature. About 20 in the hot air drawing furnace
It takes 2 seconds to 3 minutes. The draw ratio is preferably 5 times or more, more preferably 6 times or more. The drawn fiber is subjected to a heat treatment for achieving a fixed length or shrinkage, if necessary. The fiber thus obtained is further crimped or oiled if necessary.

The feature of the present invention is that P obtained by the above-mentioned method is used.
After heat-treating the VA fiber by tensioning to reduce the weight,
It is to obtain carbonaceous fibers by carbonization. It is important to perform heat treatment by tensioning from the viewpoint of shortening the heat treatment, and it is important to use PVA-based fibers heat-treated by tensioning for carbonization treatment or subsequent activation treatment. It is possible to suppress the shrinkage of the fibers during the treatment or the activation treatment, and as a result, it is possible to suppress the quality unevenness, strength unevenness and the like of the finally obtained carbonaceous fibers or fibrous activated carbon.

The temperature of the heat treatment depends on the form of the raw material fiber,
It is appropriately selected depending on the presence or absence of addition of a dehydration catalyst and the intended use of the finally obtained carbonaceous fiber or fibrous activated carbon.
The temperature is preferably 50 ° C. or higher and 300 ° C. or lower. However, if a rapid heat treatment is performed at a temperature higher than the melting point, it may melt. Therefore, when processing at a high temperature, it is effective to apply a thermal gradient and raise the temperature in one step or in multiple steps. The heat treatment method may be a continuous method or a batch method,
From the viewpoint of the productivity of the dehydration treatment, it is preferable to perform the dehydration treatment continuously.

The dehydration treatment time is appropriately determined depending on the form of the raw material fibers, the presence / absence of addition of a dehydration catalyst, the intended use of the finally obtained carbonaceous fiber or fibrous activated carbon, and the like. Sometimes not enough,
Further, if it is too long, not only the productivity is lowered, but also the shrinkage suppressing effect of the finally obtained carbonaceous fiber or fibrous activated carbon is not sufficiently expressed. Therefore, it is usually preferable to carry out the treatment for 20 seconds to 2 hours. The heat treatment atmosphere may be an oxidizing gas atmosphere or a non-oxidizing atmosphere when a dehydrating agent is used, but when not using a dehydrating agent, it is preferable to perform the heat treatment in an oxidizing atmosphere from the viewpoint of accelerating the reaction. preferable. When an oxidizing atmosphere is used, specifically, an atmosphere containing oxygen is preferable, and the oxygen concentration is 0.
5% to 21% is preferable.

To achieve weight loss efficiently, PVA
It is very effective to add, mix, and apply a dehydration catalyst to the base fiber. The dehydration catalyst is not particularly limited, but various acidic compounds are preferably used, for example. The acidic compound can be appropriately selected from known compounds, and specific examples of such a compound include sulfuric acid, hydrogen sulfate,
Examples thereof include inorganic acids such as hydrochloric acid, nitric acid, phosphoric acid, hydrogen phosphate, metaphosphoric acid, and Lewis acids such as zinc chloride, aluminum chloride, iron chloride and titanium chloride.

When there is a problem in safety and mechanical properties due to the acidity of the treatment liquid, a treatment liquid of ammonium salts neutralized with an organic amine such as ammonia may be used. Thus, by treating with the ammonium salt treatment liquid, ammonia is scattered during heating, and an inorganic acid appears to act effectively. It is known that the dehydration catalyst accelerates the dehydration reaction of PVA, is effective in shortening the heat treatment time, and can efficiently dehydrate, so that the yield is also improved. However, if the dehydration reaction is accelerated too much under no tension, the yarn will be hardened or contracted due to severe shrinkage, which is not preferable, and by heat treatment under tension, it will take about 20 seconds to 15 minutes for a short time. It becomes possible to achieve weight loss without shrinkage marks.

The amount of the dehydrating agent used is not particularly limited as long as it can accelerate the dehydration reaction. The amount of the dehydrating agent used cannot be unconditionally specified because the optimum amount varies depending on the type of the dehydrating agent, but it is usually 0.1% by weight to 20% by weight in the raw material.
Often used in weight percent. However, when producing a carbonaceous material, these dehydrating agents may decompose and volatilize in the exhaust gas to cause device corrosion, or may remain as contamination and adversely affect the product. , The amount used should be reduced as much as possible.
Preference is given to carrying out between 2% and 5% by weight.

When the weight yield is too low, the effect of suppressing shrinkage in the next step is exhibited, but the thermal decomposition reaction which is a side reaction becomes difficult to avoid, and the weight yield of the resulting carbonaceous fiber or fibrous activated carbon is increased. Will decrease, while
If the weight yield is too high, the shrinkage suppressing effect, which is the original purpose, tends not to be exhibited. Therefore, in the heat treatment, the weight yield of the dehydrated fiber to the raw material fiber is 60 to 85% by weight, preferably 65 to 75%. It is preferable to carry out the treatment so that the content thereof is wt%.

The tension applied to the fiber during heat treatment is 0.01
The range of g / dtex to 0.5 g / dtex is preferable.
As a known technique concerning tension, Japanese Patent Publication No. 40-9061
The publication describes that halogenated PVA-based fibers undergo severe thermal decomposition at around 130 ° C., and it is desirable to adjust the shrinkage by applying tension, but there is no mention of any specific conditions. However, there is no recognition that the control of tension is important in order to perform dehydration treatment in a fiber form rapidly and in a short time without shrinkage unevenness. Rather, JP-A-50-35431, 50-52320, 5
In each publication of 0-52321, 20-35% under no tension
It is disclosed that a weight-reducing formula is applied, and it is described that tension exerts an adverse effect on yarn quality.

In the present invention, the control of tension is very important in order to obtain a PVA-based carbonaceous fiber or a PVA-based activated carbon fiber which suppresses shrinkage, can be produced in a short time and is excellent in homogeneity. In view of the above, the present invention has been completed, and the carbonization treatment is performed after the weight is reduced under tension, whereby the dehydration treatment can be rapidly performed in a short time without shrinkage unevenness.

If the tension under tension is too small,
Condensation unevenness is likely to occur due to rapid dehydration, and if the tension is too high, fluff is likely to occur and the fiber may be cut, so as described above,
The amount is preferably 0.01 g / dtex to 0.5 g / dtex. When heat-treated in this tension range and dehydrated, the influence on the yarn quality is small. From the viewpoint of yarn quality and fluff suppression,
The tension is more preferably 0.02 g / dtex to 0.3 g / dtex. Since the strength of the yarn decreases as the weight decreases, the tension may be reduced stepwise.

It is not clear why the tension control within the above range is very effective in performing the dehydration treatment rapidly without shrinkage in a short time, but when the dehydration reaction proceeds rapidly,
The contraction force by contraction relaxation is very large, and it is necessary to apply tension to suppress the contraction, but as the dehydration reaction progresses, the strength of the fiber decreases, so if you apply more tension than necessary, it will break. It is presumed that it is effective to balance the tension in the range. By carbonizing the PVA-based heat-treated fiber obtained as described above,
The desired carbonaceous fiber can be obtained, and the activated carbon fiber can be obtained by subjecting the carbonaceous fiber to activation treatment.

Regarding the conditions of the carbonization treatment, it is preferable that the PVA fiber is not carbonized or violently reduced in weight during the carbonization treatment or the subsequent activation treatment.
For that purpose, it is desirable to employ the conditions for forming the aromatic ring structure to some extent, and it is usually preferable to perform the heat treatment in the range of 200 to 650 ° C. Specifically, it is recommended to use a recipe that performs oxidation treatment in an oxidizing atmosphere, a recipe that uses a catalyst such as zinc chloride, aluminum chloride, or iron chloride that promotes dehydrogenation, or halogenation that promotes the condensation reaction of aromatic rings. Although some formulations are performed, a formulation in which an oxidation treatment is performed in an oxidizing atmosphere is simple and practical.

The conditions of the carbonization treatment in an oxidizing atmosphere are not particularly limited as long as they are an atmosphere in which a sufficient cross-linking structure is introduced into the fiber and infusibilization can be achieved, but oxygen such as nitrogen gas atmosphere containing oxygen is usually used. It is carried out in a contained atmosphere. In this case, the oxygen concentration is usually appropriately selected within the range of 0.5 to 21% by volume.

The carbonaceous fiber thus obtained is suitable for use in various electrode materials, conductive materials, heat insulating materials, adsorbent materials, flameproof materials, antistatic materials, heat resistant materials, chemical resistant materials, etc. To be done. Furthermore, activated carbon fibers can be obtained by subjecting the carbonaceous fibers to activation treatment. The activation treatment step will be described below.

Regarding the activation treatment, after the above-mentioned carbonization treatment, the carbonization treatment may be temporarily cooled and then the activation treatment may be performed, or the carbonization treatment may be continuously activated. The activation method is not particularly limited as long as it can efficiently increase the specific surface area, and is generally a predetermined temperature in an atmosphere of carbon dioxide gas, water vapor, air, nitrogen or a mixed gas thereof. It is carried out in. The temperature and time of the activation treatment may be appropriately determined depending on the desired specific surface area, atmosphere and the like. For example, in the case of water vapor or carbon dioxide atmosphere, it is usually 500 to 1200 ° C, preferably 700 ° C to 1000 ° C.
The activation treatment may be performed at a temperature of several minutes to several hours, and when a combustion gas of propane gas is used, a high temperature rapid activation can be performed at a temperature of 800 to 1200 ° C. Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

[0061]

EXAMPLES Reference Example 1 PVA having a degree of polymerization of 1700 and a degree of saponification of 99.9 mol% was added to water, heated and dissolved by stirring at 80 ° C. under a nitrogen gas stream, and a spinning stock solution having a PVA concentration of 16% by weight. Was prepared. The spinning dope was spun through a spinning nozzle having a hole diameter of 0.12 mm and a number of holes of 1000 into a solidification bath of 40 ° C. containing a 30 wt% sodium sulfate aqueous solution, and wet spinning was performed. Obtained P
The VA fiber was immersed in the same solidifying bath for 1 minute and stretched 2.5 times, then immersed in a 35 wt% sodium sulfate aqueous solution at 20 ° C. for 1 minute, and the total stretching ratio was 4.5 in a saturated sodium sulfate aqueous solution at 90 ° C. The film was stretched so as to be doubled and immersed in the same bath for 30 seconds at a constant length.

Then, after washing with water at 10 ° C. for 2 minutes under running water to remove sodium sulfate, the solution is introduced into a sulfuric acid aqueous solution bath at 25 ° C. and 5% by weight (sulfuric acid and sulfuric acid in the total amount of water) of 1%. After being retained for 5 minutes, the surface and the inside of the PVA fiber were impregnated with sulfuric acid, dried with hot air at 100 ° C., and wound up. Then, the dried PVA fiber is heated to 170 ° C. for the first time.
In a hot-air oven consisting of a furnace and a second oven at 200 ° C., hot drawing was performed so that the total draw ratio was 10 times. The fineness of the obtained Itoshino is 1
It was 100 dtex, and the content of sulfuric acid in the fiber was 3% by weight.

Example 1 The fiber obtained in Reference Example 1 was dehydrated under nitrogen in a furnace at 180 ° C. under a tension of 0.04 g / dtex for a total heat treatment time of 120 seconds. The dehydrated fiber obtained was blackish brown, the weight yield based on PVA was 75% by weight, and the shrinkage in the length direction was 40%.

Then, the obtained dehydrated fiber (30c
m) in nitrogen gas containing 5% by volume of oxygen at 290 ° C.
Partial heat treatment was performed and carbonization treatment was performed. The fiber length of the obtained black carbonaceous fiber was shrunk to 25 cm, and the shrinkage rate in the carbonization treatment was 17%, but shrinkage unevenness and quality unevenness were hardly seen. In addition, the weight yield is 57
% By weight.

The black carbonaceous fiber was placed in an activation furnace adjusted to 930 ° C. by a combustion gas of propane (mainly composed of H ₂ O and CO ₂ ) and activated for 30 minutes. After activation, the fibers were washed with running water and dried to give fibrous activated carbon. The fiber length of the obtained fibrous activated carbon was shrunk to 20 cm, and the shrinkage ratio in the activation treatment was 20%, but shrinkage unevenness and quality unevenness were hardly seen. Further, the weight yield with respect to the raw material fiber is 15% by weight, and B measured by the nitrogen adsorption amount
ET specific surface area is 1600 m ² / g, JIS K1474
The amount of I ₂ adsorbed measured in accordance with the above was 1645 mg / g.

Examples 2 to 4 and Comparative Examples 1 to 4 The same procedure as in Example 1 was carried out except that 10 fibers obtained in Reference Example 1 were bundled into a bundle and 11,000 dtex was used (Example 2). ). In addition, raw material fineness, heat treatment conditions,
The tension was changed as shown in Table 1, and the same procedure as in Example 1 was performed (Examples 3 to 4 and Comparative Examples 1 to 4). The results are shown in Table 1 and Table 2 together with Example 1.

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[Table 1]

[0068]

[Table 2]

Comparative Example 5 In accordance with Example 1 of JP-A-59-187624, PVA having a degree of polymerization of 1700 was spun by an ordinary wet spinning method to form a filament of 1800d / 1000f. Then
The fiber is used as a dehydrating agent with ammonium sulfate and hydrogen sulfate 2
After 50 g of ammonium was retained in an aqueous solution obtained by dissolving 50 g of each in 1000 g of water for 5 seconds, the solution was squeezed and dried in a 105 ° C. dryer for 3 minutes. Dehydrant deposition amount is 5% by weight / P
It was a VA fiber.

This dehydrating agent-attached PVA fiber was heated in a hot air dryer at 210 ° C. for 30 minutes in the air without tension.
The obtained PVA fiber was blackish brown, the weight yield from the raw material was 72% by weight, and the shrinkage ratio in the length direction was 50%. Further, a black fibrous carbonaceous material was obtained by heat treatment at 300 ° C. for 60 minutes in the air without tension. The yield from the raw material is 52% by weight, and the shrinkage rate in carbonization is 17%
Met.

Then, the obtained fibrous carbonaceous material is
Combustion gas of propane (H_TwoO, CO _TwoIs the main component)
Charge into an activation furnace adjusted to 930 ° C and activate for 30 minutes.
It was treated lively. The shrinkage ratio in the activation treatment was 20%.
After activation, the fibers are washed with running water and dried to form fibrous activated carbon.
did. The weight yield of the obtained activated carbon with respect to the raw material fiber is
11 wt%, BET specific surface area measured by nitrogen adsorption amount is 1
460m^Two/ G, measured according to JIS K1474
The amount of I2 adsorbed was 1530 mg / g.

Comparative Example 6 A bundle of 10 fibers was bundled and 18000 dtex
PVA fiber was manufactured according to Example 1 of JP-A-59-187624 except that the above was used. As a result, the shrinkage ratio in the length direction after heating for 30 minutes in the air without tension was 48.
It was found that the shrinkage unevenness was very large at 55% and the fiber length of the final product activated carbon fiber was very uneven.

[0073]

Industrial Applicability According to the present invention, inexpensive PVA-based carbonaceous fiber or fibrous activated carbon which is excellent in quality can be industrially produced from inexpensive PVA-based fiber as a raw material. The carbonaceous fiber obtained by the present invention can be suitably used by itself as various electrode materials, conductive materials, heat insulating materials, adsorbent materials, flameproof materials, antistatic materials, heat resistant materials, chemical resistant materials and the like. The carbonaceous fiber can be made into activated carbon fiber by further activating treatment, and the obtained fibrous activated carbon is used for water purifier, air cleaner, gas adsorption, water treatment, decolorization. For cigarette filters,
It is useful as an electrode material for secondary batteries, an electrode material for electrolytic capacitors, an electrode material for electric double layer capacitors, and the like.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4G146 AA01 AA06 AB06 BA13 BB01                       BB05 BC02 BC18 BD02 BD05                 4L037 AT11 CS03 CS06 FA01 PA46                       PC06 PC08 PS03 PS12 PS17                       UA01 UA04 UA15 UA20

Claims (6)

[Claims] 1. A method for producing a carbonaceous fiber from polyvinyl alcohol fiber as a raw material, which comprises carbonizing after reducing the weight to 60% by weight or more and 85% by weight or less under tension. Manufacturing method. 2. The method for producing a carbonaceous fiber according to claim 1, wherein the raw material is polyvinyl alcohol fiber to which a dehydrating agent is attached. 3. The method for producing a carbonaceous fiber according to claim 1, wherein the weight reduction under the tension is during dehydration. 4. The tension under the tension is 0.01 g / d.
It is tex-0.5g / dtex, The manufacturing method of the carbonaceous fiber in any one of Claims 1-3. 5. A carbonaceous fiber obtained by the method according to claim 1. 6. An activated carbon fiber obtained by activating the carbonaceous fiber according to claim 5 in an oxidizing atmosphere or in the presence of steam.